Method for supporting plurality of transmission time intervals in wireless communication system and apparatus therefor

ABSTRACT

A method for supporting carrier aggregation and a short transmission time interval (sTTI) in a wireless communication system according to an embodiment of the present invention is performed by a terminal, and may comprise a step of reporting the maximum number of component carriers supporting a combination of downlink (DL) and uplink (UL) sTTI lengths, in units of bands or band combinations.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for supporting a pluralityof transmission time intervals (TTIs).

BACKGROUND ART

The latency of packet data is one of important performance metrics. Toreduce the latency of packet data and provide faster Internet access toan ender user is one of challenging issues in designing thenext-generation mobile communication system called new radio accesstechnology (RAT) as well as long term evolution (LTE). The presentdisclosure is intended to deal with uplink transmission such astransmission of a hybrid automatic repeat request (HARQ) feedback oruplink data in a wireless communication system supporting latencyreduction.

The present disclosure is intended to deal with carrier aggregation in awireless communication system supporting latency reduction.

DISCLOSURE Technical Problem

The present disclosure relates to a user equipment (UE) operation forsupporting capability reporting of a UE supporting a plurality oftransmission time intervals (TTIs) in carrier aggregation (CA) and arelated UE operation according to CA and the plurality of TTIs.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present disclosure, a method of supporting carrieraggregation (CA) and a short transmission time interval (sTTI) in awireless communication system, performed by a user equipment (UE),includes reporting a maximum number of component carriers (CCs)supporting a downlink (DL) and uplink (UL) sTTI length combination on aper-band basis or per-band combination basis.

Additionally or alternatively, the method may include receiving a DLsignal or transmitting a UL signal in a CC supporting at least one DLand UL sTTI length combination configured for the UE among the reportedDL and UL sTTI length combinations.

Additionally or alternatively, the maximum number of CCs supporting theat least one DL and UL sTTI length combination may be provided for eachof DL and UL.

Additionally or alternatively, the method may include information abouta processing time supported for each of the reported one or more DL andUL sTTI length combinations on a per-band basis or per-band combinationbasis.

Additionally or alternatively, the method may receiving a CAconfiguration for fewer CCs than the maximum number of CCs.

Additionally or alternatively, the maximum number of CCs may be reportedindependently for each of a CA case and a non-CA case.

Additionally or alternatively, the method may receiving informationabout an sTTI-based CC to be monitored by the UE from a network.

Additionally or alternatively, the method may include receivinginformation about a numerology-based CC to be monitored by the UE from anetwork, when the UE is operating with a predetermined numerology.

Additionally or alternatively, the maximum number of CCs may be based ona minimum or maximum processing time assumed for a predeterminedsTTI-based operation.

Additionally or alternatively, the method may include reportinginformation about a maximum number of layers for spatial multiplexing inDL, supported by the UE or information about a maximum number of layersfor spatial multiplexing in UL, supported by the UE.

In another aspect of the present disclosure, a UE for supporting CA andan sTTI in a wireless communication system includes a receiver and atransmitter, and a processor configured to control the receiver and thetransmitter. The processor is configured to report a maximum number ofCCs supporting a DL and UL sTTI length combination on a per-band basisor per-band combination basis.

Additionally or alternatively, the processor may be configured toreceive a DL signal or transmit a UL signal in a CC supporting at leastone DL and UL sTTI length combination configured for the UE among thereported DL and UL sTTI length combinations.

Additionally or alternatively, the maximum number of CCs supporting theat least one DL and UL sTTI length combination may be provided for eachof DL and UL.

Additionally or alternatively, the processor may be configured to reportinformation about a processing time supported for each of the reportedone or more DL and UL sTTI length combinations on a per-band basis orper-band combination basis.

Additionally or alternatively, the processor may be configured toreceive a CA configuration for fewer CCs than the maximum number of CCs.

Additionally or alternatively, the maximum number of CCs may be reportedindependently for each of a CA case and a non-CA case.

Additionally or alternatively, the processor may be configured toreceive information about an sTTI-based CC to be monitored by the UEfrom a network.

Additionally or alternatively, the processor may be configured toreceive information about a numerology-based CC to be monitored by theUE from a network, when the UE is operating with a predeterminednumerology.

Additionally or alternatively, the maximum number of CCs may be based ona minimum or maximum processing time assumed for a predeterminedsTTI-based operation.

Additionally or alternatively, the processor may be configured to reportinformation about a maximum number of layers for spatial multiplexing inDL, supported by the UE or information about a maximum number of layersfor spatial multiplexing in UL, supported by the UE.

The aforementioned solutions are just a part of embodiments of thepresent disclosure. Various embodiments to which technicalcharacteristics of the present disclosure are reflected can be drawn andunderstood based on detail explanation on the present disclosure to bedescribed in the following by those skilled in the correspondingtechnical field.

Advantageous Effects

According to the embodiments of the present disclosure, carrieraggregation may be performed efficiently.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 is a diagram for an example of a radio frame structure used inwireless communication system;

FIG. 2 is a diagram for an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system;

FIG. 3 is a diagram for an example of a downlink (DL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 4 is a diagram for an example of an uplink (UL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 5 illustrates an operation of a user equipment (UE) according to anembodiment of the present disclosure; and

FIG. 6 is a block diagram for a device configured to implementembodiment(s) of the present disclosure.

MODES FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The accompanying drawings illustrate exemplaryembodiments of the present disclosure and provide a more detaileddescription of the present disclosure. However, the scope of the presentdisclosure should not be limited thereto.

In some cases, to prevent the concept of the present disclosure frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

In the present disclosure, a user equipment (UE) is fixed or mobile. TheUE is a device that transmits and receives user data and/or controlinformation by communicating with a base station (BS). The term ‘UE’ maybe replaced with ‘terminal equipment’, ‘Mobile Station (MS)’, ‘MobileTerminal (MT)’, ‘User Terminal (UT)’, ‘Subscriber Station (SS)’,‘wireless device’, ‘Personal Digital Assistant (PDA)’, ‘wireless modem’,‘handheld device’, etc. A BS is typically a fixed station thatcommunicates with a UE and/or another BS. The BS exchanges data andcontrol information with a UE and another BS. The term ‘BS’ may bereplaced with ‘Advanced Base Station (ABS)’, ‘Node B’, ‘evolved-Node B(eNB)’, ‘Base Transceiver System (BTS)’, ‘Access Point (AP)’,‘Processing Server (PS)’, etc. In the following description, BS iscommonly called eNB.

In the present disclosure, a node refers to a fixed point capable oftransmitting/receiving a radio signal to/from a UE by communication withthe UE. Various eNBs can be used as nodes. For example, a node can be aBS, NB, eNB, pico-cell eNB (PeNB), home eNB (HeNB), relay, repeater,etc. Furthermore, a node may not be an eNB. For example, a node can be aradio remote head (RRH) or a radio remote unit (RRU). The RRH and RRUhave power levels lower than that of the eNB. Since the RRH or RRU(referred to as RRH/RRU hereinafter) is connected to an eNB through adedicated line such as an optical cable in general, cooperativecommunication according to RRH/RRU and eNB can be smoothly performedcompared to cooperative communication according to eNBs connectedthrough a wireless link. At least one antenna is installed per node. Anantenna may refer to an antenna port, a virtual antenna or an antennagroup. A node may also be called a point. Unlink a conventionalcentralized antenna system (CAS) (i.e. single node system) in whichantennas are concentrated in an eNB and controlled an eNB controller,plural nodes are spaced apart at a predetermined distance or longer in amulti-node system. The plural nodes can be managed by one or more eNBsor eNB controllers that control operations of the nodes or schedule datato be transmitted/received through the nodes. Each node may be connectedto an eNB or eNB controller managing the corresponding node via a cableor a dedicated line. In the multi-node system, the same cell identity(ID) or different cell IDs may be used for signal transmission/receptionthrough plural nodes. When plural nodes have the same cell ID, each ofthe plural nodes operates as an antenna group of a cell. If nodes havedifferent cell IDs in the multi-node system, the multi-node system canbe regarded as a multi-cell (e.g. macro-cell/femto-cell/pico-cell)system. When multiple cells respectively configured by plural nodes areoverlaid according to coverage, a network configured by multiple cellsis called a multi-tier network. The cell ID of the RRH/RRU may beidentical to or different from the cell ID of an eNB. When the RRH/RRUand eNB use different cell IDs, both the RRH/RRU and eNB operate asindependent eNBs.

In a multi-node system according to the present disclosure, which willbe described below, one or more eNBs or eNB controllers connected toplural nodes can control the plural nodes such that signals aresimultaneously transmitted to or received from a UE through some or allnodes. While there is a difference between multi-node systems accordingto the nature of each node and implementation form of each node,multi-node systems are discriminated from single node systems (e.g. CAS,conventional MIMO systems, conventional relay systems, conventionalrepeater systems, etc.) since a plurality of nodes providescommunication services to a UE in a predetermined time-frequencyresource. Accordingly, embodiments of the present disclosure withrespect to a method of performing coordinated data transmission usingsome or all nodes can be applied to various types of multi-node systems.For example, a node refers to an antenna group spaced apart from anothernode by a predetermined distance or more, in general. However,embodiments of the present disclosure, which will be described below,can even be applied to a case in which a node refers to an arbitraryantenna group irrespective of node interval. In the case of an eNBincluding an X-pole (cross polarized) antenna, for example, theembodiments of the preset disclosure are applicable on the assumptionthat the eNB controls a node composed of an H-pole antenna and a V-poleantenna.

A communication scheme through which signals are transmitted/receivedvia plural transmit (Tx)/receive (Rx) nodes, signals aretransmitted/received via at least one node selected from plural Tx/Rxnodes, or a node transmitting a downlink signal is discriminated from anode transmitting an uplink signal is called multi-eNB MIMO or CoMP(Coordinated Multi-Point Tx/Rx). Coordinated transmission schemes fromamong CoMP communication schemes can be categorized into JP (JointProcessing) and scheduling coordination. The former may be divided intoJT (Joint Transmission)/JR (Joint Reception) and DPS (Dynamic PointSelection) and the latter may be divided into CS (CoordinatedScheduling) and CB (Coordinated Beamforming). DPS may be called DCS(Dynamic Cell Selection). When JP is performed, more variouscommunication environments can be generated, compared to other CoMPschemes. JT refers to a communication scheme by which plural nodestransmit the same stream to a UE and JR refers to a communication schemeby which plural nodes receive the same stream from the UE. The UE/eNBcombine signals received from the plural nodes to restore the stream. Inthe case of JT/JR, signal transmission reliability can be improvedaccording to transmit diversity since the same stream is transmittedfrom/to plural nodes. DPS refers to a communication scheme by which asignal is transmitted/received through a node selected from plural nodesaccording to a specific rule. In the case of DPS, signal transmissionreliability can be improved because a node having a good channel statebetween the node and a UE is selected as a communication node.

In the present disclosure, a cell refers to a specific geographical areain which one or more nodes provide communication services. Accordingly,communication with a specific cell may mean communication with an eNB ora node providing communication services to the specific cell. Adownlink/uplink signal of a specific cell refers to a downlink/uplinksignal from/to an eNB or a node providing communication services to thespecific cell. A cell providing uplink/downlink communication servicesto a UE is called a serving cell. Furthermore, channel status/quality ofa specific cell refers to channel status/quality of a channel or acommunication link generated between an eNB or a node providingcommunication services to the specific cell and a UE. In 3GPP LTE-Asystems, a UE can measure downlink channel state from a specific nodeusing one or more CSI-RSs (Channel State Information Reference Signals)transmitted through antenna port(s) of the specific node on a CSI-RSresource allocated to the specific node. In general, neighboring nodestransmit CSI-RS resources on orthogonal CSI-RS resources. When CSI-RSresources are orthogonal, this means that the CSI-RS resources havedifferent subframe configurations and/or CSI-RS sequences which specifysubframes to which CSI-RSs are allocated according to CSI-RS resourceconfigurations, subframe offsets and transmission periods, etc. whichspecify symbols and subcarriers carrying the CSI RSs.

In the present disclosure, PDCCH (Physical Downlink ControlChannel)/PCFICH (Physical Control Format Indicator Channel)/PHICH(Physical Hybrid automatic repeat request Indicator Channel)/PDSCH(Physical Downlink Shared Channel) refer to a set of time-frequencyresources or resource elements respectively carrying DCI (DownlinkControl Information)/CFI (Control Format Indicator)/downlink ACK/NACK(Acknowlegement/Negative ACK)/downlink data. In addition, PUCCH(Physical Uplink Control Channel)/PUSCH (Physical Uplink SharedChannel)/PRACH (Physical Random Access Channel) refer to sets oftime-frequency resources or resource elements respectively carrying UCI(Uplink Control Information)/uplink data/random access signals. In thepresent disclosure, a time-frequency resource or a resource element(RE), which is allocated to or belongs toPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH, is referred to as aPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. In the followingdescription, transmission of PUCCH/PUSCH/PRACH by a UE is equivalent totransmission of uplink control information/uplink data/random accesssignal through or on PUCCH/PUSCH/PRACH. Furthermore, transmission ofPDCCH/PCFICH/PHICH/PDSCH by an eNB is equivalent to transmission ofdownlink data/control information through or onPDCCH/PCFICH/PHICH/PDSCH.

FIG. 1 illustrates an exemplary radio frame structure used in a wirelesscommunication system. FIG. 1(a) illustrates a frame structure forfrequency division duplex (FDD) used in 3GPP LTE/LTE-A and FIG. 1(b)illustrates a frame structure for time division duplex (TDD) used in3GPP LTE/LTE-A.

Referring to FIG. 1, a radio frame used in 3GPP LTE/LTE-A has a lengthof 10 ms (307200Ts) and includes 10 subframes in equal size. The 10subframes in the radio frame may be numbered. Here, Ts denotes samplingtime and is represented as Ts=1/(2048*15 kHz). Each subframe has alength of lms and includes two slots. 20 slots in the radio frame can besequentially numbered from 0 to 19. Each slot has a length of 0.5 ms. Atime for transmitting a subframe is defined as a transmission timeinterval (TTI). Time resources can be discriminated by a radio framenumber (or radio frame index), subframe number (or subframe index) and aslot number (or slot index).

The radio frame can be configured differently according to duplex mode.Downlink transmission is discriminated from uplink transmission byfrequency in FDD mode, and thus the radio frame includes only one of adownlink subframe and an uplink subframe in a specific frequency band.In TDD mode, downlink transmission is discriminated from uplinktransmission by time, and thus the radio frame includes both a downlinksubframe and an uplink subframe in a specific frequency band.

Table 1 shows DL-UL configurations of subframes in a radio frame in theTDD mode.

TABLE 1 Downlink- DL-UL to-Uplink con- Switch-point Subframe numberfiguration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 ms D S U U UD D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6  5ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes threefields of DwPTS (Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS(Uplink Pilot TimeSlot). DwPTS is a period reserved for downlinktransmission and UpPTS is a period reserved for uplink transmission.

Table 2 shows special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Extended Normal Extended Special Normal cycliccyclic cyclic subframe cyclic prefix prefix in prefix in prefix inconfiguration DwPTS in uplink uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — —

FIG. 2 illustrates an exemplary downlink/uplink slot structure in awireless communication system. Particularly, FIG. 2 illustrates aresource grid structure in 3GPP LTE/LTE-A. A resource grid is presentper antenna port.

Referring to FIG. 2, a slot includes a plurality of OFDM (OrthogonalFrequency Division Multiplexing) symbols in the time domain and aplurality of resource blocks (RBs) in the frequency domain. An OFDMsymbol may refer to a symbol period. A signal transmitted in each slotmay be represented by a resource grid composed of N_(RB) ^(DL/UL)*N_(sc)^(RB) subcarriers and N_(symb) ^(DL/UL) OFDM symbols. Here, N_(RB) ^(DL)denotes the number of RBs in a downlink slot and N_(RB) ^(UL) denotesthe number of RBs in an uplink slot. N_(RB) ^(DL) and N_(RB) ^(UL)respectively depend on a DL transmission bandwidth and a UL transmissionbandwidth. N_(symb) ^(DL) denotes the number of OFDM symbols in thedownlink slot and N_(symb) ^(UL) denotes the number of OFDM symbols inthe uplink slot. In addition, N_(sc) ^(RB) denotes the number ofsubcarriers constructing one RB.

An OFDM symbol may be called an SC-FDM (Single Carrier FrequencyDivision Multiplexing) symbol according to multiple access scheme. Thenumber of OFDM symbols included in a slot may depend on a channelbandwidth and the length of a cyclic prefix (CP). For example, a slotincludes 7 OFDM symbols in the case of normal CP and 6 OFDM symbols inthe case of extended CP. While FIG. 2 illustrates a subframe in which aslot includes 7 OFDM symbols for convenience, embodiments of the presentdisclosure can be equally applied to subframes having different numbersof OFDM symbols. Referring to FIG. 2, each OFDM symbol includes N_(RB)^(DL/UL)*N_(sc) ^(RB) subcarriers in the frequency domain. Subcarriertypes can be classified into a data subcarrier for data transmission, areference signal subcarrier for reference signal transmission, and nullsubcarriers for a guard band and a direct current (DC) component. Thenull subcarrier for a DC component is a subcarrier remaining unused andis mapped to a carrier frequency (f0) during OFDM signal generation orfrequency up-conversion. The carrier frequency is also called a centerfrequency.

An RB is defined by N_(symb) ^(DL/UL) (e.g. 7) consecutive OFDM symbolsin the time domain and N_(sc) ^(RB) (e.g. 12) consecutive subcarriers inthe frequency domain. For reference, a resource composed by an OFDMsymbol and a subcarrier is called a resource element (RE) or a tone.Accordingly, an RB is composed of N_(symb) ^(DL/UL) Each RE in aresource grid can be uniquely defined by an index pair (k, l) in a slot.Here, k is an index in the range of 0 to N_(symb) ^(Dl/UL)*N_(sc)^(RB)−1 in the frequency domain and 1 is an index in the range of 0 toN_(symb) ^(DL/UL)−1.

Two RBs that occupy N_(sc) ^(RB) consecutive subcarriers in a subframeand respectively disposed in two slots of the subframe are called aphysical resource block (PRB) pair. Two RBs constituting a PRB pair havethe same PRB number (or PRB index). A virtual resource block (VRB) is alogical resource allocation unit for resource allocation. The VRB hasthe same size as that of the PRB. The VRB may be divided into alocalized VRB and a distributed VRB depending on a mapping scheme of VRBinto PRB. The localized VRBs are mapped into the PRBs, whereby VRBnumber (VRB index) corresponds to PRB number. That is, n_(PRB)=n_(VRB)is obtained. Numbers are given to the localized VRBs from 0 to N_(VRB)^(DL)−1, and N_(VRB) ^(DL)=N_(RB) ^(DL) is obtained. Accordingly,according to the localized mapping scheme, the VRBs having the same VRBnumber are mapped into the PRBs having the same PRB number at the firstslot and the second slot. On the other hand, the distributed VRBs aremapped into the PRBs through interleaving. Accordingly, the VRBs havingthe same VRB number may be mapped into the PRBs having different PRBnumbers at the first slot and the second slot. Two PRBs, which arerespectively located at two slots of the subframe and have the same VRBnumber, will be referred to as a pair of VRBs.

FIG. 3 illustrates a downlink (DL) subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 3, a DL subframe is divided into a control region anda data region. A maximum of three (four) OFDM symbols located in a frontportion of a first slot within a subframe correspond to the controlregion to which a control channel is allocated. A resource regionavailable for PDCCH transmission in the DL subframe is referred to as aPDCCH region hereinafter. The remaining OFDM symbols correspond to thedata region to which a physical downlink shared chancel (PDSCH) isallocated. A resource region available for PDSCH transmission in the DLsubframe is referred to as a PDSCH region hereinafter. Examples ofdownlink control channels used in 3GPP LTE include a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc. ThePCFICH is transmitted at a first OFDM symbol of a subframe and carriesinformation regarding the number of OFDM symbols used for transmissionof control channels within the subframe. The PHICH is a response ofuplink transmission and carries an HARQ acknowledgment (ACK)/negativeacknowledgment (NACK) signal.

Control information carried on the PDCCH is called downlink controlinformation (DCI). The DCI contains resource allocation information andcontrol information for a UE or a UE group. For example, the DCIincludes a transport format and resource allocation information of adownlink shared channel (DL-SCH), a transport format and resourceallocation information of an uplink shared channel (UL-SCH), paginginformation of a paging channel (PCH), system information on the DL-SCH,information about resource allocation of an upper layer control messagesuch as a random access response transmitted on the PDSCH, a transmitcontrol command set with respect to individual UEs in a UE group, atransmit power control command, information on activation of a voiceover IP (VoIP), downlink assignment index (DAI), etc. The transportformat and resource allocation information of the DL-SCH are also calledDL scheduling information or a DL grant and the transport format andresource allocation information of the UL-SCH are also called ULscheduling information or a UL grant. The size and purpose of DCIcarried on a PDCCH depend on DCI format and the size thereof may bevaried according to coding rate. Various formats, for example, formats 0and 4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3Afor downlink, have been defined in 3GPP LTE. Control information such asa hopping flag, information on RB allocation, modulation coding scheme(MCS), redundancy version (RV), new data indicator (NDI), information ontransmit power control (TPC), cyclic shift demodulation reference signal(DMRS), UL index, channel quality information (CQI) request, DLassignment index, HARQ process number, transmitted precoding matrixindicator (TPMI), precoding matrix indicator (PMI), etc. is selected andcombined based on DCI format and transmitted to a UE as DCI.

In general, a DCI format for a UE depends on transmission mode (TM) setfor the UE. In other words, only a DCI format corresponding to aspecific TM can be used for a UE configured in the specific TM.

A PDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel. The CCE corresponds to a plurality of resource element groups(REGs). For example, a CCE corresponds to 9 REGs and an REG correspondsto 4 REs. 3GPP LTE defines a CCE set in which a PDCCH can be located foreach UE. A CCE set from which a UE can detect a PDCCH thereof is calleda PDCCH search space, simply, search space. An individual resourcethrough which the PDCCH can be transmitted within the search space iscalled a PDCCH candidate. A set of PDCCH candidates to be monitored bythe UE is defined as the search space. In 3GPP LTE/LTE-A, search spacesfor DCI formats may have different sizes and include a dedicated searchspace and a common search space. The dedicated search space is aUE-specific search space and is configured for each UE. The commonsearch space is configured for a plurality of UEs. Aggregation levelsdefining the search space is as follows.

TABLE 3 Search Space Aggregation Size Number of PDCCH Type Level L [inCCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 416 4 8 16 2

A PDCCH candidate corresponds to 1, 2, 4 or 8 CCEs according to CCEaggregation level. An eNB transmits a PDCCH (DCI) on an arbitrary PDCCHcandidate with in a search space and a UE monitors the search space todetect the PDCCH (DCI). Here, monitoring refers to attempting to decodeeach PDCCH in the corresponding search space according to all monitoredDCI formats. The UE can detect the PDCCH thereof by monitoring pluralPDCCHs. Since the UE does not know the position in which the PDCCHthereof is transmitted, the UE attempts to decode all PDCCHs of thecorresponding DCI format for each subframe until a PDCCH having the IDthereof is detected. This process is called blind detection (or blinddecoding (BD)).

The eNB can transmit data for a UE or a UE group through the dataregion. Data transmitted through the data region may be called userdata. For transmission of the user data, a physical downlink sharedchannel (PDSCH) may be allocated to the data region. A paging channel(PCH) and downlink-shared channel (DL-SCH) are transmitted through thePDSCH. The UE can read data transmitted through the PDSCH by decodingcontrol information transmitted through a PDCCH. Informationrepresenting a UE or a UE group to which data on the PDSCH istransmitted, how the UE or UE group receives and decodes the PDSCH data,etc. is included in the PDCCH and transmitted. For example, if aspecific PDCCH is CRC (cyclic redundancy check)-masked having radionetwork temporary identify (RNTI) of “A” and information about datatransmitted using a radio resource (e.g., frequency position) of “B” andtransmission format information (e.g., transport block size, modulationscheme, coding information, etc.) of “C” is transmitted through aspecific DL subframe, the UE monitors PDCCHs using RNTI information anda UE having the RNTI of “A” detects a PDCCH and receives a PDSCHindicated by “B” and “C” using information about the PDCCH.

A reference signal (RS) to be compared with a data signal is necessaryfor the UE to demodulate a signal received from the eNB. A referencesignal refers to a predetermined signal having a specific waveform,which is transmitted from the eNB to the UE or from the UE to the eNBand known to both the eNB and UE. The reference signal is also called apilot. Reference signals are categorized into a cell-specific RS sharedby all UEs in a cell and a modulation RS (DM RS) dedicated for aspecific UE. A DM RS transmitted by the eNB for demodulation of downlinkdata for a specific UE is called a UE-specific RS. Both or one of DM RSand CRS may be transmitted on downlink. When only the DM RS istransmitted without CRS, an RS for channel measurement needs to beadditionally provided because the DM RS transmitted using the sameprecoder as used for data can be used for demodulation only. Forexample, in 3GPP LTE(-A), CSI-RS corresponding to an additional RS formeasurement is transmitted to the UE such that the UE can measurechannel state information. CSI-RS is transmitted in each transmissionperiod corresponding to a plurality of subframes based on the fact thatchannel state variation with time is not large, unlike CRS transmittedper subframe.

FIG. 4 illustrates an exemplary uplink subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 4, a UL subframe can be divided into a control regionand a data region in the frequency domain. One or more PUCCHs (physicaluplink control channels) can be allocated to the control region to carryuplink control information (UCI). One or more PUSCHs (Physical uplinkshared channels) may be allocated to the data region of the UL subframeto carry user data.

In the UL subframe, subcarriers spaced apart from a DC subcarrier areused as the control region. In other words, subcarriers corresponding toboth ends of a UL transmission bandwidth are assigned to UCItransmission. The DC subcarrier is a component remaining unused forsignal transmission and is mapped to the carrier frequency f0 duringfrequency up-conversion. A PUCCH for a UE is allocated to an RB pairbelonging to resources operating at a carrier frequency and RBsbelonging to the RB pair occupy different subcarriers in two slots.Assignment of the PUCCH in this manner is represented as frequencyhopping of an RB pair allocated to the PUCCH at a slot boundary. Whenfrequency hopping is not applied, the RB pair occupies the samesubcarrier.

The PUCCH can be used to transmit the following control information.

Scheduling Request (SR): This is information used to request a UL-SCHresource and is transmitted using On-Off Keying (OOK) scheme.

HARQ ACK/NACK: This is a response signal to a downlink data packet on aPDSCH and indicates whether the downlink data packet has beensuccessfully received. A 1-bit ACK/NACK signal is transmitted as aresponse to a single downlink codeword and a 2-bit ACK/NACK signal istransmitted as a response to two downlink codewords. HARQ-ACK responsesinclude positive ACK (ACK), negative ACK (NACK), discontinuoustransmission (DTX) and NACK/DTX. Here, the term HARQ-ACK is usedinterchangeably with the term HARQ ACK/NACK and ACK/NACK.

Channel State Indicator (CSI): This is feedback information about adownlink channel. Feedback information regarding MIMO includes a rankindicator (RI) and a precoding matrix indicator (PMI).

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission correspond to SC-FDMA symbols otherthan SC-FDMA symbols of the subframe, which are used for referencesignal transmission. In the case of a subframe in which a soundingreference signal (SRS) is configured, the last SC-FDMA symbol of thesubframe is excluded from the SC-FDMA symbols available for controlinformation transmission. A reference signal is used to detect coherenceof the PUCCH. The PUCCH supports various formats according toinformation transmitted thereon.

Table 4 shows the mapping relationship between PUCCH formats and UCI inLTE/LTE-A.

TABLE 4 Number of bits per PUCCH Modulation subframe, format scheme M_(bit) Usage Etc. 1 N/A N/A SR (Scheduling Request) 1a BPSK 1 ACK/NACKor One codeword SR + ACK/ NACK 1b QPSK 2 ACK/NACK or Two codeword SR +ACK/ NACK 2 QPSK 20 CQI/PMI/RI Joint coding ACK/NACK (extended CP) 2aQPSK + BPSK 21 CQI/PMI/RI + Normal CP only ACK/NACK 2b QPSK + QPSK 22CQI/PMI/RI + Normal CP only ACK/NACK 3 QPSK 48 ACK/NACK or SR + ACK/NACK or CQI/ PMI/RI + ACK/NACK

Referring to Table 4, PUCCH formats 1/1a/lb are used to transmitACK/NACK information, PUCCH format 2/2a/2b are used to carry CSI such asCQI/PMFRI and PUCCH format 3 is used to transmit ACK/NACK information.

Reference Signal (RS)

When a packet is transmitted in a wireless communication system, signaldistortion may occur during transmission since the packet is transmittedthrough a radio channel. To correctly receive a distorted signal at areceiver, the distorted signal needs to be corrected using channelinformation. To detect channel information, a signal known to both atransmitter and the receiver is transmitted and channel information isdetected with a degree of distortion of the signal when the signal isreceived through a channel. This signal is called a pilot signal or areference signal.

When data is transmitted/received using multiple antennas, the receivercan receive a correct signal only when the receiver is aware of achannel state between each transmit antenna and each receive antenna.Accordingly, a reference signal needs to be provided per transmitantenna, more specifically, per antenna port.

Reference signals can be classified into an uplink reference signal anda downlink reference signal. In LTE, the uplink reference signalincludes:

i) a demodulation reference signal (DMRS) for channel estimation forcoherent demodulation of information transmitted through a PUSCH and aPUCCH; and

ii) a sounding reference signal (SRS) used for an eNB to measure uplinkchannel quality at a frequency of a different network.

The downlink reference signal includes:

i) a cell-specific reference signal (CRS) shared by all UEs in a cell;

ii) a UE-specific reference signal for a specific UE only;

iii) a DMRS transmitted for coherent demodulation when a PDSCH istransmitted;

iv) a channel state information reference signal (CSI-RS) for deliveringchannel state information (CSI) when a downlink DMRS is transmitted;

v) a multimedia broadcast single frequency network (MBSFN) referencesignal transmitted for coherent demodulation of a signal transmitted inMB SFN mode; and

vi) a positioning reference signal used to estimate geographic positioninformation of a UE.

Reference signals can be classified into a reference signal for channelinformation acquisition and a reference signal for data demodulation.The former needs to be transmitted in a wide band as it is used for a UEto acquire channel information on downlink transmission and received bya UE even if the UE does not receive downlink data in a specificsubframe. This reference signal is used even in a handover situation.The latter is transmitted along with a corresponding resource by an eNBwhen the eNB transmits a downlink signal and is used for a UE todemodulate data through channel measurement. This reference signal needsto be transmitted in a region in which data is transmitted.

In order to satisfy requirements for various application fields, it maybe considered to configure various transmission time intervals (TTIs)(or various TTI lengths) for all or a specific physical channel in thenext-generation system. More characteristically, a TTI during which aphysical channel such as a PDCCH/PDSCH/PUSCH/PUCCH is transmitted may beset to be less than lmsec to reduce latency for communication between aneNB and a UE according to a scenario (such a PDCCH/PDSCH/PUSCH/PUCCH isreferred to as an sPDCCH/sPDSCH/sPUSCH/sPUCCH). For a single UE ormultiple UEs, a plurality of physical channels may exist in a singlesubframe (e.g., lmsec), and have different TTIs (or TTI lengths). Thefollowing embodiments will be described in the context of an LTE system,for the convenience of description. A TTI may be lmsec (normal TTI), thelength of a normal subframe used in the LTE system, and a short TTI is aTTI shorter than the normal TTI, spanning one or more OFDM or SC-FDMAsymbols. While a short TTI (i.e., a TTI shorter than a legacy onesubframe) is taken for the convenience of description, the key featuresof the present disclosure may be extended to a TTI longer than onesubframe or equal to or longer than lms. Characteristically, the keyfeatures of the present disclosure may also be extended to a short TTIwhich is introduced to the next-generation system by increasing asubcarrier spacing. Although the present disclosure is described in thecontext of LTE, for convenience, the same thing is applicable to atechnology using a different waveform/frame structure such as new radioaccess technology (RAT). In general, the present disclosure is based onthe assumption of an sTTI (<1 msec), a longTTI (=1 msec), and alongerTTl (>1 msec). While a plurality of UL channels having differentTTI lengths/numerologies/processing times have been described above, itis apparent that the following embodiments may be extended to aplurality of UL/DL channels to which different service requirements,latencies, and scheduling units are applied.

CA Using sTTI

It may be regulated that a UE reports whether it supports an sTTIoperation (or different/additional numerology operation) by capabilitysignaling. In this case, it may be regulated that if the sTTI operation(or different/additional numerology operation) is configured for the UE,the configured operation is applied to all carriers. It may be regulatedthat the UE reports whether it supports the sTTI operation (ordifferent/additional numerology operation) depending on whether itactually implements CA, or whether it supports the sTTI operation (ordifferent/additional numerology operation) for each of numbers ofactually aggregated CCs for CA (or each range including a group ofnumbers of CCs actually aggregated CCs for CA).

Further, the UE may report whether it supports a specific sTTI length(group) or a specific DL/UL sTTI length combination by capabilitysignaling. Further, the UE may report whether it supports a specificDL/UL numerology (group) or a specific DL/UL numerology combination bycapability signaling.

It may be regulated that the UE reports whether it supports the sTTIoperation (or different/additional numerology operation) on a per-bandbasis or a per-band combination basis (a per band per band-combinationbasis). According to the proposal of the present disclosure, the UE mayreport the capability of supporting an sTTI operation (ordifferent/additional numerology operation) independently for each of CCsavailable for CA, thereby enabling more flexible UE implementation. Forexample, a UE with low processing power may report that the UE supportsthe sTTI operation only for one of two CCs available for CA, while a UEwith high processing power may report that the UE supports the sTTIoperation for both of the CCs.

If the sTTI operation is supported for a specific band or bandcombination, a specific capability may also be reported. Specifically,it may be regulated that the UE reports a supported TTI length for eachband or band combination and/or a supported processing time for eachspecific sTTI length (group) or DL/UL sTTI length combination. Forexample, the UE capability report of a supported TTI length and/or asupported processing time may be a report that the UE supports aprocessing time such as a DL data-to-DL HARQ-ACK and/or UL grant-to-ULdata timing of an (n+6) sTTI, for a specific band or band combination,in the case of a 2-symbol TTI. Characteristically, a different supportedprocessing time may be set for each DL sTTI length (group) or each ULsTTI length (group) or each DL and UL combination.

If a different/additional numerology operation is supported for aspecific band or band combination, a specific capability may also bereported. Specifically, it may be regulated that the UE reports asupported numerology for each band or band combination and/or asupported processing for each specific numerology (group) or eachspecific DL/UL numerology combination.

The processing time may include a DL data-to-DL HARQ-ACK timing and/or aUL grant-to-UL data timing.

It may be regulated that the UE reports a maximum number of CCssupporting an sTTI operation (or different/additional numerologyoperation) in a specific band, on a per-band or per-band combinationbasis. If this signaling is introduced, the UE may report moreelaborately whether the UE supports the sTTI operation (ordifferent/additional numerology operation) for CCs of intra-bandcontiguous CA. For example, even when intra-band contiguous CA isperformed by using bandwidth class C in band x, it is possible tosupport the sTTI operation (or different/additional numerologyoperation) only for a part of a plurality of CCs included in band x.

Further, it may be regulated that the UE reports a maximum number of CCssupporting a specific sTTI length (group) or a specific DL/UL sTTIlength combination in a specific band on a per-band or per-bandcombination basis. Further, it may be regulated that the UE reports amaximum number of CCs supporting a specific numerology (group) or anumerology group or a specific DL/UL numerology combination in aspecific band on a per-band or per-band combination basis.

Further, it may be regulated that the UE reports the capability ofsupporting the sTTI operation (or different/additional numerologyoperation) independently on a per-CC basis, even for CCs ofnon-contiguous intra-band CA. Specifically, it may be regulated thatinformation indicating whether the sTTI operation (ordifferent/additional numerology operation) operation is supported on aper-band or per-band combination basis and/or information about asupported TTI length and/or numerology and/or a supported processingtime and/or a maximum number of CCs supporting the sTTI operation (ordifferent/additional numerology operation)operation is configuredindependently for each intra-band CC. Characteristically, a differentsupported processing time may be configured for each DL sTTIlength/numerology (group) or UL sTTI length/numerology (group) or DL andUL combination. The processing time may include a DL data-to-DL HARQ-ACKtiming and/or a UL grant-to-UL data timing.

As the number of CCs aggregated for CA decreases, a CA-enabled UE mayhave more extra processing power, and support an sTTI operation (ordifferent/additional numerology operation) for more CCs with the extraprocessing power. Accordingly, it may be regulated that for each numberof CCs actually aggregated for CA, a maximum number of CCs for which thesTTI operation (or different/additional numerology operation) issupported is reported or pre-defined/pre-agreed.

Further, it may be regulated if a CA-enabled UE is configured with aconfiguration related to an sTTI operation (or different/additionalnumerology operation), the UE is configured only with a CA operation fora predetermined number of or fewer CCs. It may be regulated if a

CA-enabled UE is configured with a configuration related to an sTTIoperation (or different/additional numerology operation), one of a CAoperation and the sTTI operation (or different/additional numerologyoperation) is disabled.

Further, it may be regulated that different maximum numbers of CCssupporting the sTTI operation (or different/additional numerologyoperation) when CA is performed and CCs supporting the sTTI operation(or different/additional numerology operation) when CA is not performedare reported independently by the UE, or pre-defined/pre-agreed.

It may be regulated that if the UE is configured with the sTTI operation(or different/additional numerology operation) on a per-band or per-CCbasis, a maximum transport block (TB) size and/or a maximum timingadvance (TA) and/or a maximum number of transmission layers and/or amaximum number of transmission PRBs is additionally limited (notsupported due to strict scheduling restriction) on a per-band or per-CCbasis. The restriction may be pre-agreed or signaled. Particularly, therestriction may be different independently for each numerology (e.g.,each TTI length or subcarrier spacing). Further, it may be regulatedthat if the sTTI operation (or different/additional numerologyoperation) is configured for the UE, the UE reports a supported maximumTB size and/or a supported maximum TA and/or a maximum number oftransmission layers and/or a maximum number of transmission PRBs on aper-band or per-CC basis.

As described above, the UE may report a maximum number of CCs supportingthe sTTI operation. It may occur that a large number of DL CCs and asmall number of UL CCs support the sTTI operation. Therefore, it may beregulated that the UE independently reports a maximum number of DL CCssupporting the sTTI operation and a maximum number of UL CCs supportingthe sTTI operation. Characteristically, the UE may transmit thecapability signaling on a per-band or per-band combination basis.Further, the UE may transmit the capability signaling independently foreach specific sTTI length (group) or specific DL/UL sTTI lengthcombination.

Likewise, it may be regulated that the UE independently reports amaximum number of DL CCs supporting a specific processing time and amaximum number of UL CCs supporting the specific processing time.Characteristically, the UE may transmit the capability signaling on aper-band or per-band combination basis. Further, the UE may transmit thecapability signaling independently for each specific sTTI length (group)or specific DL/UL sTTI length combination.

If the UE reports a maximum number of DL/UL CCs supporting the sTTIoperation or the number of DL/UL CCs supporting the sTTI operation isset in any other manner, the network may configure cells supporting thesTTI operation. In another method, the sTTI operation may be configureduniformly for all cells of a PUCCH group. In this case, the UE shouldmonitor an sPDCCH in all cells.

To overcome this problem, it may be regulated that information about thenumber of cells in which the UE should monitor an sPDCCH and/or theindexes (or carrier indicator field (CIF) indexes) of the cells in whichthe UE should monitor an sPDCCH, among active cells is pre-configured byhigher-layer signaling. Further, the information about the number and/orindexes (or CIF indexes) of cells in which the UE should monitor ansPDCCH may be configured for the UE, while the UE is operating with apredetermined or default numerology. Alternatively, the informationabout the number and/or indexes (or CIF indexes) of cells in which theUE should monitor an sPDCCH may be configured for the UE, while the UEis operating with a numerology other than the predetermined or defaultnumerology.

Characteristically, the information about the indexes (or CIF indexes)of cells in which the UE should monitor an sPDCCH may be configured byhigher-layer signaling or DCI. More characteristically, the informationabout the indexes (or CIF indexes) of cells in which the UE shouldmonitor an sPDCCH may be configured differently for each sPDCCH RB set.For example, if the maximum number of (DL) CCs in which the UE supportsthe sTTI operation is 2, the indexes of cells in which the UE shouldmonitor an sPDCCH in a 5-cell CA situation may be configured as DL CCs 0and 1 by higher-layer signaling. If the UE is configured to monitor ansPDCCH in more than two cells, the UE may ignore the configuration andmonitor an sPDCCH in as many cells as the capability of the UE.Alternatively, it may be regulated that the UE does not expect to beconfigured to monitor an sPDCCH in more cells than the capability of theUE. The above proposal may be useful, when an sTTI operation isconfigured uniformly for all cells of a PUCCH group and/or the sTTIoperation is configured UE-specifically.

In another method, an sTTI may be configured for all cells or a subsetof cells, and as many carriers as supported by the UE may be activateddynamically or statically. The activation may be performed by a MAC CEor DCI. In this case, it may be assumed that the correspondingtransmission is performed in a legacy TTI or a common search space(CSS).

Signaling of UE Capability Regarding Maximum Number of CCs for sTTIOperation

Signaling a capability regarding a maximum number of CCs for which theUE supports an sTTI operation may amount to reporting a maximum numberof (DL or UL) CCs for which the UE supports the sTTI operation on theassumption of a specific processing time for a specific sTTI lengthcombination. More characteristically, the capability signaling may be toreport the maximum number of (DL or UL) CCs for which the UE supportsthe sTTI operation on the assumption of a minimum or maximum processingtime for the specific sTTI length combination. The network may considerbased on the report that the UE is capable of supporting the sTTIoperation at least for the reported number of CCs for the specific sTTIlength combination. Herein, the processing time may include a DLdata-to-DL HARQ-ACK timing and/or a UL grant-to-UL data timing, andthese two values may be equal or different. For example, for acombination of different DL and UL sTTI lengths, the two values may beset to be different. The minimum processing time may be the smallest ofprocessing time candidates configurable for the UE, for the specificsTTI length combination.

MIMO Capability for sTTI Operation

According to the current LTE standard, capability signaling indicating amaximum number of UE-supported layers for spatial multiplexing in aspecific band is defined as follows.

TS36.331 v14.2.1 (2017.03) CA-MIMO-ParametersUL-r10 ::= SEQUENCE {ca-BandwidthClassUL-r10 CA-BandwidthClass-r10,supportedMIMO-CapabilityUL-r10 MIMO-CapabilityUL-r10  OPTIONAL }CA-MIMO-ParametersDL-r10 ::= SEQUENCE { ca-BandwidthClassDL-r10CA-BandwidthClass-r10, supportedMIMO-CapabilityDL-r10MIMO-CapabilityDL-r10  OPTIONA } MIMO-CapabilityUL-r10 ::= ENUMERATED{twoLayers, fourLayers} MIMO-CapabilityDL-r10 ::= ENUMERATED {twoLayers,fourLayers, eightLayers}

TABLE 5 UE-EUTRA-Capability field descriptions MIMO-CapabilityDL Thenumber of supported layers for spatial multiplexing in DL. The field maybe absent for category 0 and category 1 UE in which case the number ofsupported layers is 1. MIMO-CapabilityUL The number of supported layersfor spatial multiplexing in UL. Absence of the field means that thenumber of supported layers is 1.

The sTTI operation requires a shorter processing time (e.g., 4 ms) thana processing time corresponding to the legacy 1-ms TTI. Herein, theprocessing time may include a DL PDSCH-to-DL HARQ-ACK timing and/or a ULgrant-to-UL data timing. Therefore, the UE may be designed to supportfewer layers for spatial multiplexing than the maximum number ofsupported layers for spatial multiplexing in the legacy 1-ms TTIoperation. To allow the network to know this situation, it may beregulated that when the UE reports a maximum number of supported layersfor spatial multiplexing in DL and/or UL, the UE reports the maximumnumber of supported layers independently for each target block errorrate (BLER) and/or service type and/or numerology and/or TTI lengthand/or DL and UL TTI length combination and/or processing timeconfigured by higher-layer signaling (or indicated by Ll signaling) orfor each of combinations thereof. Further, the capability signaling maybe transmitted independently on a per-band or per-band combinationbasis.

Since examples of the above proposed methods may be included as one ofmethods of implementing the present disclosure, it is apparent that theexamples may be regarded as proposed methods. Further, the foregoingproposed methods may be implemented independently, or some of themethods may be implemented in combination (or merged). Further, it maybe regulated that information indicating whether the proposed methodsare applied (or information about the rules of the proposed methods) isindicated to a UE by a pre-defined signal (or a physical-layer orhigher-layer signal) by an eNB.

FIG. 5 illustrates an operation according to an embodiment of thepresent disclosure.

FIG. 5 relates to a method of supporting CA and an sTTI in a wirelesscommunication system. The method may be performed by a UE. The UE mayreport a maximum number of CCs supporting one or more DL and UL sTTIlength combinations on a per-band or per-band combination basis (S510).The maximum number of CCs supporting the one or more DL and UL sTTIlength combinations may be provided for each of DL and UL.

Further, the UE may receive a DL signal or transmit a UL signal in a CCsupporting at least one configured DL and UL sTTI length combinationamong the reported DL and UL sTTI length combinations (S520).

The UE may report information about a processing time supported for eachof the reported one or more DL and UL sTTI length combinations on aper-band basis or per-band combination basis. Further, the UE mayreceive a CA configuration for fewer CCs than the maximum number of CCs.

The maximum number of CCs may be reported independently for each of a CAcase and a non-CA case.

The UE may receive information about an sTTI-based CC to be monitored bythe UE from a network.

When the UE is operating with a predetermined numerology, the UE mayreceive information about a numerology-based CC to be monitored by theUE from the network.

The maximum number of CCs may be based on a minimum or maximumprocessing time assumed for a predetermined sTTI-based operation.

The UE may report information about a maximum number of layers forspatial multiplexing in DL, supported by the UE or information about amaximum number of layers for spatial multiplexing in UL, supported bythe UE.

FIG. 6 is a block diagram of a transmitting device 10 and a receivingdevice 20 configured to implement exemplary embodiments of the presentdisclosure. Referring to FIG. 6, the transmitting device 10 and thereceiving device 20 respectively include transmitter/receiver 13 and 23for transmitting and receiving radio signals carrying information, data,signals, and/or messages, memories 12 and 22 for storing informationrelated to communication in a wireless communication system, andprocessors 11 and 21 connected operationally to the transmitter/receiver13 and 23 and the memories 12 and 22 and configured to control thememories 12 and 22 and/or the transmitter/receiver 13 and 23 so as toperform at least one of the above-described embodiments of the presentdisclosure.

The memories 12 and 22 may store programs for processing and control ofthe processors 11 and 21 and may temporarily storing input/outputinformation. The memories 12 and 22 may be used as buffers. Theprocessors 11 and 21 control the overall operation of various modules inthe transmitting device 10 or the receiving device 20. The processors 11and 21 may perform various control functions to implement the presentdisclosure. The processors 11 and 21 may be controllers,microcontrollers, microprocessors, or microcomputers. The processors 11and 21 may be implemented by hardware, firmware, software, or acombination thereof. In a hardware configuration, application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs), orfield programmable gate arrays (FPGAs) may be included in the processors11 and 21. If the present disclosure is implemented using firmware orsoftware, firmware or software may be configured to include modules,procedures, functions, etc. performing the functions or operations ofthe present disclosure. Firmware or software configured to perform thepresent disclosure may be included in the processors 11 and 21 or storedin the memories 12 and 22 so as to be driven by the processors 11 and21.

The processor 11 of the transmitting device 10 is scheduled from theprocessor 11 or a scheduler connected to the processor 11 and codes andmodulates signals and/or data to be transmitted to the outside. Thecoded and modulated signals and/or data are transmitted to thetransmitter/receiver 13. For example, the processor 11 converts a datastream to be transmitted into K layers through demultiplexing, channelcoding, scrambling and modulation. The coded data stream is alsoreferred to as a codeword and is equivalent to a transport block whichis a data block provided by a MAC layer. One transport block (TB) iscoded into one codeword and each codeword is transmitted to thereceiving device in the form of one or more layers. For frequencyup-conversion, the transmitter/receiver 13 may include an oscillator.The transmitter/receiver 13 may include Nt (where Nt is a positiveinteger) transmit antennas.

A signal processing process of the receiving device 20 is the reverse ofthe signal processing process of the transmitting device 10. Under thecontrol of the processor 21, the transmitter/receiver 23 of thereceiving device 10 receives RF signals transmitted by the transmittingdevice 10. The transmitter/receiver 23 may include Nr receive antennasand frequency down-converts each signal received through receiveantennas into a baseband signal. The transmitter/receiver 23 may includean oscillator for frequency down-conversion. The processor 21 decodesand demodulates the radio signals received through the receive antennasand restores data that the transmitting device 10 wishes to transmit.

The transmitter/receiver 13 and 23 include one or more antennas. Anantenna performs a function of transmitting signals processed by thetransmitter/receiver 13 and 23 to the exterior or receiving radiosignals from the exterior to transfer the radio signals to thetransmitter/receiver 13 and 23. The antenna may also be called anantenna port. Each antenna may correspond to one physical antenna or maybe configured by a combination of more than one physical antennaelement. A signal transmitted through each antenna cannot be decomposedby the receiving device 20. A reference signal (RS) transmitted throughan antenna defines the corresponding antenna viewed from the receivingdevice 20 and enables the receiving device 20 to perform channelestimation for the antenna, irrespective of whether a channel is asingle RF channel from one physical antenna or a composite channel froma plurality of physical antenna elements including the antenna. That is,an antenna is defined such that a channel transmitting a symbol on theantenna may be derived from the channel transmitting another symbol onthe same antenna. A transmitter/receiver supporting a MIMO function oftransmitting and receiving data using a plurality of antennas may beconnected to two or more antennas.

In embodiments of the present disclosure, a UE serves as thetransmission device 10 on uplink and as the receiving device 20 ondownlink. In embodiments of the present disclosure, an eNB serves as thereceiving device 20 on uplink and as the transmission device 10 ondownlink.

The transmitting device and/or the receiving device may be configured asa combination of one or more embodiments of the present disclosure.

The detailed description of the exemplary embodiments of the presentdisclosure has been given to enable those skilled in the art toimplement and practice the disclosure. Although the disclosure has beendescribed with reference to the exemplary embodiments, those skilled inthe art will appreciate that various modifications and variations can bemade in the present disclosure without departing from the spirit orscope of the disclosure described in the appended claims. For example,those skilled in the art may use each construction described in theabove embodiments in combination with each other. Accordingly, thedisclosure should not be limited to the specific embodiments describedherein, but should be accorded the broadest scope consistent with theprinciples and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The present disclosure may be used for a wireless communicationapparatus such as a UE, a relay and an eNB.

1. A method of supporting carrier aggregation (CA) and a shorttransmission time interval (sTTI) in a wireless communication system,performed by a user equipment (UE), the method comprising: reporting amaximum number of component carriers (CCs) supporting a downlink (DL)and uplink (UL) sTTI length combination on a per-band basis or per-bandcombination basis.
 2. The method according to claim 1, furthercomprising: receiving a DL signal or transmitting a UL signal in a CCsupporting at least one DL and UL sTTI length combination configured forthe UE among the reported DL and UL sTTI length combinations.
 3. Themethod according to claim 1, wherein the maximum number of CCssupporting the at least one DL and UL sTTI length combination isprovided for each of DL and UL.
 4. The method according to claim 1,further comprising: reporting information about a processing timesupported for each of the one or more reported DL and UL sTTI lengthcombinations on a per-band basis or per-band combination basis.
 5. Themethod according to claim 1, further comprising: receiving a CAconfiguration for fewer CCs than the maximum number of CCs.
 6. Themethod according to claim 1, wherein the maximum number of CCs isreported independently for each of a CA case and a non-CA case.
 7. Themethod according to claim 1, further comprising: receiving informationabout an sTTI-based CC to be monitored by the UE from a network.
 8. Themethod according to claim 1, further comprising: receiving informationabout a numerology-based CC to be monitored by the UE from a network,when the UE is operating with a predetermined numerology.
 9. The methodaccording to claim 1, wherein the maximum number of CCs is based on aminimum or maximum processing time assumed for a predeterminedsTTI-based operation.
 10. The method according to claim 1, furthercomprising: reporting information about a maximum number of layers forspatial multiplexing in DL, supported by the UE or information about amaximum number of layers for spatial multiplexing in UL, supported bythe UE.
 11. A user equipment (UE) for supporting carrier aggregation(CA) and a short transmission time interval (sTTI) in a wirelesscommunication system, the UE comprising: a receiver and a transmitter;and a processor configured to control the receiver and the transmitter,wherein the processor is configured to report a maximum number ofcomponent carriers (CCs) supporting a downlink (DL) and uplink (UL) sTTIlength combination on a per-band basis or per-band combination basis.12. The UE according to claim 11, wherein the processor is configured toreceive a DL signal or transmit a UL signal in a CC supporting at leastone DL and UL sTTI length combination configured for the UE among thereported DL and UL sTTI length combinations.
 13. The UE according toclaim 11, wherein the maximum number of CCs supporting the at least oneDL and UL sTTI length combination is provided for each of DL and UL. 14.The UE according to claim 1, wherein the processor is configured toreport information about a processing time supported for each of thereported one or more DL and UL sTTI length combinations on a per-bandbasis or per-band combination basis.
 15. The UE according to claim 11,wherein the processor is configured to receive a CA configuration forfewer CCs than the maximum number of CCs.
 16. The UE according to claim11, wherein the maximum number of CCs is reported independently for eachof a CA case and a non-CA case.
 17. The UE according to claim 11,wherein the processor is configured to receive information about ansTTI-based CC to be monitored by the UE from a network.
 18. The UEaccording to claim 11, wherein the processor is configured to receiveinformation about a numerology-based CC to be monitored by the UE from anetwork, when the UE is operating with a predetermined numerology. 19.The UE according to claim 11, wherein the maximum number of CCs is basedon a minimum or maximum processing time assumed for a predeterminedsTTI-based operation.
 20. The UE according to claim 11, wherein theprocessor is configured to report information about a maximum number oflayers for spatial multiplexing in DL, supported by the UE orinformation about a maximum number of layers for spatial multiplexing inUL, supported by the UE.